SP beta is a temperate phage of Bacillus subtilis. It can carry out specialized transduction of bacterial genes close to the prophase attachment site. We have developed methods of isolating bacterial strains in which SP beta has inserted its DNA into the bacterial chromosome at sites distant from the normal attachment site; genes close to these unusual sites can be transduced. Bacteria lysogenic for SP beta defective transducing prophages are diploid (usually heterogenotic) for the bacterial genes carried by the phage. Bacteria doubly lysogenic for a defective transducing phage and for a complete phage release both types of particles following induction. SP beta therefore seems to be a candidate as a tool for gene transfer and gene cloning in B. subtilis, in many of the ways that phage lambda has been used in Escherichia coli. We propose to produce a restriction endonuclease cleavage map of phage SP beta. We will then produce radioactive probes of endonuclease-generated fragments of SP beta DNA, and use these probes to determine the order of the fragments in a lysogen of SP beta to learn if the prophage is a cyclic permutation of the phage DNA. The probes will then be used to study the DNA content of at least one defective transducing phage, to learn which fragments are present in the defective phage and which are missing. The DNA of the defective transducing phage will also be annealed with marked SP beta DNA and examined by heteroduplex analysis with the electron microscope. This should allow us to determine the structure of the defective phage particles' DNA. Various bacterial strains lysogenic for different defective transducing phages will be tested with the radioactive probes to determine which portions of the phage genome are present on each defective phage. The same defective prophages are being studied by marker-rescue experiments to learn what phage genes they contain. Comparison of the two studies will allow us to assign particular phage genes to particular restriction endonuclease fragments.